I'm thinking about "What is an example of a foreign currency in the world today, that can be exchanged for U.S. dollars? And describe at least one country where that currency is being used as money now".

In my thinking,

In the China,

the Chinese Yuan (RMB), as a foreign currency that is able to exchange for the US Dollar (USD). The Chinese use the term "yuan" () to classify their own currency. China is a country with a very long history, so does its currency. Since ancient times, they had used shells as a currency. Later on, because of a lack of shells, they switched to use small bones and stones instead. After that, they learned how to cast copper coins and used them widely. By the mid-20th century, the Chinese Yuan (RMB) was released and used popularly in China. According to the current currency converter, 1.00 USD equals 6.61 RMB. In the past 20 years, however, their currency was higher that a US dollar worth of about 8.26. Nowadays, China uses two types of money similar to America: banknotes and coins. There are 7-banknote-denomination: from 1 RMB to 100 RMB, and 4-coin-denomination: from 0.1 RMB to 1 RMB. There are many countries that their governments allow RMB transactions in commerce. For example, my home country (Vietnam), the first Southeast Asian country to officially trade in Chinese currency in seven border provinces.

These days, Apple Inc. is releasing its latest smartphone, the iPhone12s; and I want to talk about its price in two markets, America and China. At an Apple store in the US, you will need to pay about $1,000, which is equivalent to around 6,500 for an iPhone 12 Pro; however, based on the Apple Store price list in China, the phone costs you up to 8,500 (~ 2,000 more expensive). This is a significant gap for the same good but sold in two different countries. Besides the tax fees, there are several reasons that cause this difference, such as that some features of the iPhone only exist in the US but not in another country.

In the UK,

The UK or British pound is the currency of the UK. It can easily be exchanged for US dollars. The UK pound is the currency of the United Kingdom and all its possessions and territories such as the British Virgin Islands, Guernsey, Pitcairn, St. Helena. The UK is the best example where the pound sterling is the only currency that is used as money. All products are priced in UK pounds. Foreigners wishing to buy British products in the UK will have to convert their money for UK pounds at the going exchange rate. Countries wishing to import from the UK will also have to do the same. For example, if the British price is 100, then people with the US currency as their money will have to acquire the pounds at the spot exchange rate. If the exchange rate is 1 = $1.32, then $132 will have to be converted into 100.

If you compare the prices of several items in the US and UK, 1 liter (1 qt.) of whole fat milk 0.86, 2 letters of Coca-Cola 1.951 liter (1 qt.) of whole fat milk. If you convert this into dollars, milk is $1.13 and 2 letters of Coca-Cola are $2.57. However, actually, 1 liter (1 qt.) It is $0.88, 2 letters of Coca-Cola $1.98 in the US. It was $115 per pound on March 18, 2020. If the pound continues to rise, continuous price increases will reduce the value of money, decrease the purchasing power of the people, and may cause inflation.

I would like to know "a numerical example of how currency appreciation of the U.S. dollar (compared to the currency in the UK and China) could be seen in the future in the Foreign Exchange Market" in these posts.

I do not have some idea...